Last February, two balloons that were launched from Reno, Nevada, flew to Northern California. Along the way, as planned, they released a small amount of sulfur dioxide, a gas that has a cooling effect when erupting volcanoes release it.

In their six-to-eight-hour journey, according to a High Country News flight-path analysis, the balloons crossed the airspace of at least five tribes, including the Colfax-Todds Valley Consolidated Tribe. But when I called Pam Cubbler, the tribe’s vice chair and lead cultural preservation officer, in April, she said it was the first she’d heard of it.

Her response? “What a strange thing to do.”

Make Sunsets, the company behind the balloons, believes that releasing sulfur dioxide could mitigate global heating. Cubbler, however, had questions: What research supported this? What does sulfur dioxide do to the environment, and can it be cleaned up? “It’s the unknown that concerns me,” she said.

Make Sunsets wants to release sulfur dioxide into the stratosphere to reflect sunlight away from the earth — a type of solar geoengineering known as stratospheric aerosol injection. If implemented at a large-enough scale, it could help cool the planet, but it wouldn’t halt rising greenhouse gas emissions, according to the Intergovernmental Panel on Climate Change’s 2021 report. When used at a small scale, as Make Sunsets is currently doing, there’s little risk, but at a larger scale, it could cause acid rain, respiratory damage and abrupt changes to the water cycle, including torrential rains and droughts. It could prevent a heat wave in one location while causing a drought in another — even widen the Antarctic ozone hole.

Make Sunsets, Cubbler thinks, is trying to play God. “They’re taking over the way of the Creator,” she said — and they never consulted the tribe. “They should have contacted us, and I think they should have contacted every single tribe in that path,” she said.

People can have the power to change global temperatures.

Make Sunsets was founded by Luke Iseman and Andrew Song, two men who’d worked at venture-backed tech startups. Their company is backed by venture capital and angel investors. They sell “cooling credits” that individuals or companies can purchase, like carbon credits; one cooling credit corresponds to the release of at least one gram of sulfur dioxide. Iseman and Song’s website describes them as “self-starters” who are “not afraid to take on big challenges and pursue ambitious goals, even in the face of adversity.”

When the Wall Street Journal asked Iseman if he worried about “playing God,” he paraphrased a quote from the writer Stewart Brand: “We are as gods and we need to get good at it.” He added, “You can hand-wring about how crazy it is. … People can have the power to change global temperatures, and yeah, I get it. The other version of that is we can buy the world time to decarbonize while minimizing harm in the meantime.”

When I spoke to Iseman, he noted that the world is racing past its climate-change goal — limiting warming to below 1.5 degrees Celsius (2.7 degrees Fahrenheit). Iseman is driven by fear of a hotter planet, “where regions of the world with millions of people in them become uninhabitable unless you have AC, and if the AC breaks, you die. Like, literally, that kind of climate horror.” The World Meteorological Association recently warned that the earth is likely to breach the 1.5-degree limit by 2027. Iseman believes solar geoengineering is necessary to save lives. “We’ve only seen the slightest start of it,” he said. 

Iseman said his company has already made a positive impact by prompting conversations about solar geoengineering: “The more people think about this idea, and the more they read about it, and the more they research it, the more likely it is that they will support it.” But the company’s early tests and methods have also prompted backlash: Following Make Sunsets’ launch in Baja California Sur — done without government permission — Mexico banned real-world solar geoengineering experiments.

Iseman acknowledged that he lacked data showing the balloons’ effectiveness, but added that, in large amounts, sulfur dioxide has a demonstrated cooling effect. Scientists and experts I spoke with, though, said Make Sunsets’ claims regarding their cooling credits have little scientific basis.“You cannot be reckless when it comes to our climate systems,” said Shuchi Talati, founder and executive director of the Alliance for Just Deliberation on Solar Geoengineering. There is no consensus on solar geoengineering, she said, and “the fact that there’s this much hubris around claiming that deployment is the right answer is really unjust, to be quite honest.” Talati fears the company’s activities and financial ambitions could erode trust in this nascent field.

“The more people think about this idea, and the more they read about it, and the more they research it, the more likely it is that they will support it.”

Gernot Wagner, climate economist at Columbia Business School and founding co-director of Harvard’s solar geoengineering research project, warned that the combination of incentives — low cost, potential profitability and the urgency of climate change — encourages private companies focused on financial gain, rather than serious research, to dive into geoengineering when scientists should be leading the way. “This can’t be a race toward who flies more balloons sooner,” he said. “That would be really, really bad.” 

And the affected communities should be included in the conversation, Talati said. Someday, she said, they may want to use the technology, but the company’s actions are “taking away the rights of communities to be part of decisions that dictate their own futures.

 “It’s essentially another form of colonialism.”


Luke Iseman, co-founder of the solar geoengineering startup Make Sunsets, holds a weather balloon filled with helium, air and sulfur dioxide at a park in Reno, Nevada, last February. Credit: Balazs Gardi

MANY CLIMATE VENTURES,including mining projects, renewable energy and carbon offsets, are developed on sensitive lands or waterways without tribal approval, in what has been dubbed “green colonialism.” Another solar geoengineering project, SCoPEx, was halted in 2021, when the Saami Council in the Nordic region called for it to be shut down, citing environmental concerns and a lack of consultation. Energy storage projects and solar developments in Washington — developed as part of the state’s green boom — have faced opposition because they threaten tribal resources.

It’s part of a long history of private companies’ general disregard of tribal authority, said Will Haney, a lawyer and a citizen of the Seminole Nation of Oklahoma. “There’s this mentality of ‘we’re going to move through and move fast and break things,’” with little consideration for Indigenous people.

Solar geoengineering is not currently regulated, but if Make Sunsets begins to have an environmental impact, regulatory hurdles will arise, including environmental reviews and tribal consultation, according to Edward Parson, environmental law professor and faculty director of the Emmett Institute on Climate Change and the Environment at the UCLA School of Law.

Make Sunsets could face fines if a tribal court found it had infringed on tribal airspace, although tribal authority wanes the higher you go. “If something crashes on tribal land,” Haney explained, “there’s a stronger nexus for tribes to be able to assert that jurisdiction with a good possibility of it being upheld, ultimately, when it’s appealed. If we’re talking about flying over tribal lands, especially at very high altitudes, it’s going to be very difficult for even the most legally developed tribe to assert jurisdiction over that.” But if chemicals are released and fall on tribal land, it’s possible that “the tribes have some kind of claim against the folks who are doing this.”

“There’s this mentality of ‘we’re going to move through and move fast and break things,’”with little consideration for Indigenous people.

Cubbler pointed out that tribes face significant hurdles when they try to engage in climate mitigation. After a massive wildfire in fall 2022, the Colfax-Todds Valley Consolidated Tribe restored the use of cultural burns to prevent future conflagrations. But the tribe had to prove itself to government agencies first, and Cubbler wondered what hurdles Make Sunsets had cleared to launch balloons. Tribes, she said, should have a say over their airspace — or at least be informed about what’s going on up there.

“It would just be nice to have the notification if there’s something that is being spread over our territory.” 

Three of the other tribal nations the balloons passed over — the Reno-Sparks Indian Colony, Shingle Springs Band of Miwok Indians and United Auburn Indian Community — declined to comment. But Mike DeSpain, natural resources director for the Buena Vista Rancheria of Me-Wuk Indians of California, said that companies should not fly anything over tribal land “without the tribe being well aware and approving.”

Iseman said he’ll notify tribal nations in the future, though he believes the launch was legally sound. The Reno balloons flew “above commercial aviation by a good margin,” he said, and planes release more sulfur dioxide anyway. “If I actually violated tribal airspace, I’ll be happy to pay any reasonable fine. I’m pretty confident I didn’t.

“I would be curious if the same tribes object to Reno International not notifying them of exact flight routes,” he said. Still, he acknowledged that tribal nations, like other groups heavily impacted by climate change, should get a say in climate action.   

Hilary Beaumont is a freelance investigative journalist, covering climate change, Indigenous rights and immigration. @hilarybeaumont

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This article appeared in the print edition of the magazine with the headline What to make of Make Sunsets.

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